Buffer capacity of 4% succinylated gelatin does not provide any advantages over acidic 6% hydroxyethyl starch 130/0.4 for acid–base balance during experimental mixed acidaemia in a porcine model

BACKGROUND AND OBJECTIVE:Four percent gelatine is an alkaline compound due to NH2 groups, whereas 6% hydroxyethyl starch 130/0.4 (HES130) has acidic features. We investigated whether these solutions lead to differences in acid-base balance in pigs during acidaemia and correction of pH. METHODS:Anaesthetized pigs were randomized to HES130 or gelatine infusion (n = 5 per group). Animals received acid infusion (0.4 M solution of lactic acid and HCl diluted in normal saline) and low tidal volume ventilation (6-7 mL kg, PaCO2 of 80-85 mmHg, pH 7.19-7.24). Measurements were made before and after induction of acidaemia, before and after correction of pH with haemofiltration (continuous venovenous haemofiltration) and tris-hydroxymethylaminomethane infusion. We measured parameters describing acid-base balance according to Stewartʼs approach, ketone body formation, oxygen delivery, haemodynamics, diuresis and urinary pH. RESULTS:Acid-base balance did not differ significantly between the groups. In HES130-treated pigs, the haemodilution-based drop of haemoglobin (1.4 ± 1.0 g dL, median ± SD) was paralleled by an increase in the cardiac output (0.5 ± 0.4 L min). Lacking increases in cardiac output, gelatine-treated pigs demonstrated a reduction in oxygen delivery (149.4 ± 106.0 mL min). Tris-hydroxymethylaminomethane volumes required for pH titration to desired values were significantly higher in the gelatine group (0.7 ± 0.1 mL kg h vs. HES1300.5 ± 0.2 mL kg h). CONCLUSION:The buffer capacity of gelatine did not lead to favourable differences in acid-base balance in comparison to HES130.